Bocal

From AudioLexic

A bocal is a curved, tapered metal tube, which is part of some woodwind instruments, including the bassoon and the English horn, which extends from the top of the instrument to the reed. Most bocals are made of sterling silver, and covered at the lower end with a cork sleeve, which holds the bocal tightly in the metal socket at the top of the instrument. The reed either fits directly onto the tapered end of the bocal (like a bassoon) or is tied to a metal tube which fits to the bocal (like an English horn).

For the bassoon, most newer bocals have a hole for the bassoon's "whisper" or "octave" key, to assist in playing different octaves.

Bocals are made in varying lengths, often with markings such as "1", "2" and "3", which are used to adjust the pitch of the instrument higher or lower.